... to make it "smi-corrupting" decompression-friendly.

Also add a cctest for the CSA implementation.

Bug: v8:9706
Change-Id: I1f1b0aa1b40832a0c2ce81658da316b3e442189c
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/1796802Reviewed-by: Toon Verwaest <verwaest@chromium.org>
Commit-Queue: Igor Sheludko <ishell@chromium.org>
Cr-Commit-Position: refs/heads/master@{#63674}